In a network using Multi Protocol Label Switching (MPLS), a protection technique called Fast Reroute (FRR) defined by Request for Comments (RFC) 4090 is broadly used.
FRR is one of fast failure recovery methods called Local Repair, and in FRR, for an MPLS tunnel Label Switching Path (LSP) that is to be protected (Protected LSP), a local bypass route (Backup LSP) is set in advance, to perform high-speed switching to the bypass route when a failure occurs in a link or a core node.
For example, in the case of link protection, as illustrated in FIG. 1, a Backup LSP 112 routed through nodes 106 and 107 is set between a node 102 and a node 103 for a Protected LSP 111 provided between a node 101 and a node 104. When a failure occurs in the link between the node 101 and the node 104, the path between the nodes is switched to the Backup LSP 112.
In the case of node protection, as illustrated in FIG. 2, a Backup LSP 113 routed through nodes 106-108 is set between a node 102 and a node 104 for the Protected LSP 111. When a failure occurs in the node 103, the path between the node 102 and the node 104 is switched to the Backup LSP 113.
Meanwhile, the method to set an end-to-end bypass route is called Global Repair. In this case, as illustrated in FIG. 3, a Backup LSP 114 routed through nodes 105-108 is set between the node 101 and the node 104 for the Protected LSP 111. When a failure occurs in the link between the node 101 and the node 104, the entirety of the Protected LSP 111 is switched to the Backup LSP 114.
FRR is a fast and effective protection technique, as the switching can be performed at 50 ms, and only half the number of tunnel LSPs end-to-end is required compared to Global Repair. However, while a failure in a link and a core node in an LSP path can be recovered, a failure in an edge node being the start point or the end point of a tunnel LSP cannot be recovered.
For example, in the case of an MPLS network illustrated in FIG. 4, a Protected LSP 431 is provided between an edge node 421 and an edge node 426. These edge nodes are called Provider Edge (PE). A customer device 411 communicates with a customer device 412 using the Protected LSP 431.
The protected LSP 431 includes core nodes 422-425, and a Backup LSP 432 routed through a core node 427 is provided between the node 422 and the node 423. Meanwhile, a Backup LSP 433 routed through core node 428 is provided between the node 423 and the node 425.
The node 422 corresponds to the start-point node of the LSP 432, and the node 423 corresponds to the end-point node of the Backup LSP 432 as well as the start-point node of the Backup LSP 433, and the node 425 corresponds to the end-point node of the Backup LSP 433. The start-point node of a Backup LSP is called Point of Local Repair (PLR), and the end-point node is called Merger Point (MP).
The Backup LSP 432 is used for the next hop protection targeted at the link between the start-point node 422 and the end-point node 423. Meanwhile, the Backup LSP 433 is used for the next next hop protection targeted at the link between the start-point node 423 and the node 424, the node 424, and the link between the node 424 and the end-point node 425.
Patent document 1 below relates to a communication device having an FRR function for MPLS.    Patent document 1: Japanese Laid-open Patent Publication No. 2003-124971